We have recently observed three general "trophic" phenomena on a cloned line of skeletal muscle cells: 1) An increase in cellular division, 2) An increase in the number of cells which fuse, and 3) An increase in acetylcholine receptor site density and the formation of high density clusters of receptors. The factors causing these trophic effects were found in the highest specific activities in the central nervous system and amniotic fluid. This proposal deals with efforts to study these phenomena in greater detail. The techniques to be used are light and EM autoradiography to quantify the effects on acetylcholine receptor, biochemical separation and characterization of the factors, electrophysiological techniques for studying any alteration in the excitable properties of the cells and to quantify synaptogenesis, and finally determine the extent of cellular division and differentiation. IDEN*